Couple of weeks back i got my kleemann headers installed and when we first started up the motor it wasn't idling properly.. Really rough!
The mechanic took it for a drive and when he brought it back we scanned the car and found the code p0306. So we swapped out the coil and wires between 5 and 6.... Still ended up with the same issue.
Hooked up star and noticed when the car is at idle the duty cycle for 6 is much larger then the rest of the cylinders. If you stand behind the car your clothing, skin etc will smell like GAS. if you park the car and walk behind the car you smell like gas.
Now where should i start my troubleshooting? Should i start by changing the plugs? or the injectors?
The guy that installed the headers said that i may have a problem with my injector and to run injector cleaner.
I'd be looking at the spark plug wires and the plugs themselves on cylinder 6. Could have cracked the porcelain on a plug while working in the area wrestling the headers in if they left em in while installing the headers or damaged a spark plug wire when installing/removing them. One of the wires not seated well possibly?
I don't see it throwing a cylinder 6 misfire if the O2's were somehow crossed. You'd get a multi cylinder misfire if anything or issue with it going lean or rich as the computer fought to control air fuel ratio in the banks and it was not seeing what it was requesting/expecting from the injectors.
If an O2 is the problem (I doubt it) it would be the front O2's as the post cat O2's do NOTHING except report on if the catalytic converter is operating properly. The front O2's is what the engine uses to adjust running parameters.